The online job market trace in Latin America and the Caribbean

Jobs intermediated by online platforms have become a central pillar of labour markets in Latin America and the Caribbean. Public online platforms inevitably leave digital trace data that can be used as a source of information regarding online labour supply and demand. This report explores the opportunities and challenges of the systematic use of these publicly available data. The objective is to give an overview of the volume and nature of these data, and to share the lessons learned in order to develop a research agenda that enables alternative labour market information tools to be created, based on these new sources. To provide an initial analysis of the type of information that can be drawn from this data source, this report presents the main findings from data collected from six major international labour market platforms and two global freelancing sites in late 2019 and early 2020. These platforms are Acciontrabajo (Profdir), CompuTrabajo, Jobisjob, CaribbeanJobsOnline, CaribbeanJobs, and the two global freelancing sites are Freelancer and Upwork, covering 33 countries in Latin America and the Caribbean.Introduction .-- I. Methodological considerations .-- II. Freelancing labour market .-- III. Domestic labour market .-- IV. Temporal dynamics .-- V. Further explorations .-- VI. Conclusions

Characterization of conductive multiwall carbon nanotube/polystyrene composites prepared by latex technology, Carbon 45

Abstract Conductive multiwall carbon nanotube/polystyrene (MWCNT/PS) composites are prepared based on latex technology. MWCNTs are first dispersed in aqueous solution of sodium dodecyl sulfate (SDS) driven by sonication and then mixed with different amounts of PS latex. From these mixtures MWCNT/PS composites were prepared by freeze-drying and compression molding. The dispersion of MWCNTs in aqueous SDS solution and in the PS matrix is monitored by UV-vis, transmission electron microscopy, electron tomography and scanning electron microscopy. When applying adequate preparation conditions, MWCNTs are well dispersed and homogeneously incorporated in the PS matrix. The percolation threshold for conduction is about 1.5 wt% of MWCNTs in the composites, and a maximum conductivity of about 1 S m À1 can be achieved. The approach presented can be adapted to other MWCNT/polymer latex systems

On the volume organisation of thermoplastic vulcanisates (TPVs) as revealed by scanning transmission electron microscopy (STEM) tomography

The phase organisation of thermoplastic vulcanisates (TPVs) has been analysed in detail by applying scanning transmission electron microscopy (STEM) tomography. High contrast between the crosslinked rubber (EPDM) and the isotactic polypropylene (iPP) phases has been achieved without staining the samples. STEM tomography at low-converge-angle conditions allows for the investigation of micrometre thick samples enabling analysis of dispersion and (possible) connectivity of the phases in the TPVs for ultra-large (>50 µm3) volumes. EPDM is dispersed in the iPP phase in a TPV with low EPDM content, whereas it forms a co-continuous phase in a TPV with high EPDM content. The latter could up to now not been demonstrated unambiguously and has impact on the rheological behaviour of the TPV. Moreover, it is demonstrated that zinc oxide and talc particles used as additives in the TPV formulation are located exclusively in the iPP phase of the TPV blend, which suggests that wetting of the solid particles by the relatively low viscous iPP phase during dynamic vulcanisation determines the location of these inorganic additives

High-Angle Annular Dark Field Scanning Transmission Electron Microscopy on Carbon-Based Functional Polymer Systems

Two purely carbon-based functional polymer systems were investigated by bright-field conventional transmission electron microscopy (CTEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). For a carbon black (CB) filled polymer system, HAADF-STEM provides high contrast between the CB agglomerates and the polymer matrix so that details of the interface organization easily can be revealed and assignment of the CB phase is straightforward. For a second system, the functional polymer blend representing the photoactive layer of a polymer solar cell, details of its nanoscale organization could be observed that were not accessible with CTEM. By varying the camera length in HAADF-STEM imaging, the contrast can be enhanced between crystalline and amorphous compounds due to diffraction contrast so that nanoscale interconnections between domains are identified. In general, due to its incoherent imaging characteristics HAADF-STEM allows for reliable interpretation of the data obtained

High-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) on carbon-based functional polymer systems

Two purely carbon-based functional polymer systems were investigated by bright-field conventional transmission electron microscopy (CTEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). For a carbon black (CB) filled polymer system, HAADF-STEM provides high contrast between the CB agglomerates and the polymer matrix so that details of the interface organization easily can be revealed and assignment of the CB phase is straightforward. For a second system, the functional polymer blend representing the photoactive layer of a polymer solar cell, details of its nanoscale organization could be observed that were not accessible with CTEM. By varying the camera length in HAADF-STEM imaging, the contrast can be enhanced between crystalline and amorphous compounds due to diffraction contrast so that nanoscale interconnections between domains are identified. In general, due to its incoherent imaging characteristics HAADF-STEM allows for reliable interpretation of the data obtained

Electron tomography on micrometer-thick specimens with nanometer resolution

Transmission electron microscopy (TEM) is a well-established technique to explore matter down to the atomic scale. TEM tomography methodshave been developed to obtain volume information at the mesoscopic dimensions of devices or complex mixtures of multiphase objects withnanometer resolution, but these methods are in general only applicable to relatively thin specimens with a few hundred nanometer thicknessat most. Here we introduce an approach based on scanning TEM (STEM) tomography that pushes the resolution in three dimensions downto a few nanometers for several micrometer ultrathick specimens using a conventional TEM with 300 kV accelerating voltage, and we demonstrateits versatility for materials research and nanotechnology

Carbon nanotube/isotactic polypropylene composites prepared by latex technology: Morphology analysis of CNT-induced nucleation

The crystallization behavior of isotactic polypropylene (iPP) in the vicinity of single-wall and multiwall carbon nanotubes (SWCNTs and MWCNTs) has been studied. Combined DSC and transmission electron microscopy (TEM) investigations of bulk composite materials reveal that CNTs nucleate iPP when crystallizing from the quiescent melt and that iPP crystals form a transcrystalline layer of aligned iPP lamellar crystals around the nucleating CNT. The pronounced nucleation effect and the formation of a transcrystalline layer is observed also for ultrathin film CNT/iPP samples. Corresponding diffraction studies show that in bulk as well as in the case of the ultrathin film samples only the ?-phase of iPP exists. The transcrystalline layer is highly oriented around the nucleating CNTs, and the crystallographic c-axes of the lamellae are oriented perpendicular to the long axis of the nucleating CNT, which is in contradiction to assumptions done in other studies. This crystallization behavior is discussed and a possible explanation is provided based on iPP macromolecules wrapped around rather than aligned along the CNTs prior to formation of the nucleus. © 2008 American Chemical Societ